Blast furnace coke is used as a reducing agent, a heat resource, and a supporting material in order to keep gas permeability in a blast furnace. Nowadays, there is a trend toward manufacturing high strength coke so as to realize stable operation under the condition of a low reducing agent rate. Since plural kinds (ten kinds or more) of coal are typically blended and used when blast furnace coke is manufactured, investigations regarding a method for predicting the strength of coke which is derived from a coal blend have been conducted. For example, methods (A) through (C) below are well known.
(A) Coke Strength Prediction Method Using the Strength of Coke Matrix and Fluidity as Indices
This method is based on a blending theory which predicts coke strength using two indices, which are a mean maximum reflectance of vitrinite (the average value of Ro, hereinafter, simply represented by Ro) and a Gieseler maximum fluidity (MF), as parameters for coal quality and is generally used nowadays.
(B) Coke Strength Prediction Method Using NMR
This is a coke strength prediction method using an index indicating the amount of coal plastic component which is determined using NMR (Nuclear Magnetic Resonance) and an index indicating the viscosity of coal plastic component (for example, refer to Patent Literature 1).
(C) Coke Strength Prediction Method Using a Blending Effect Coefficient as an Index
The properties of coal vary depending on an origin, a coal mine, and a coal seam, and it is pointed out that there is compatibility among different kinds of coal when different kinds of coal are blended and used to manufacture coke.
In the cases of typical coke strength prediction equations used in the methods such as those described in (A) and (B) above, since the strength of coke which is derived from coal blend consisting of two kinds of coal is predicted using weighted average values of various physical properties, there are many cases where an effect of increasing strength due to compatibility, that is, a blending effect is not predicted. On the contrary, a method for predicting a blending effect is known. According to the method, the property of coke which is derived from coal blend consisting of plural kinds of coal is predicted on the assumption that the coke is the aggregation of all the combinations of two kinds of coal selected from among the constituent coal kinds of the coke, the difference between the property of coke derived from two kinds of coal and the weighted average value of the properties of the two kinds of coke which are respectively derived from the two kinds of single coal is represented by a blending effect coefficient, and a coke strength predicting equation is obtained using the blending effect coefficients (for example, refer to Patent Literature 2). A blending effect coefficient may be obtained by actual measurement or presumption.